Rheostat.



H. E.V HEATH. RHEOSTAT. APPLIOATIOI FILED AUG. 4. 1905.

Patented Ayr. 27, l1909.

T. fo y I F U3 frm o pronision' of'an improved unit. of this @han l.; in the Construction of resistance units 1 o material as graphite and carbon, which con- :i5 ited. in the ease of the cast grids, the spe- STATES Pie i ninna' n. or m' inisfqnionnse'rrs, ein', @erweiterten nm' nnsosfism.

No. 919,575. Speeio-ton of Letters Patent. Patented April 27, 1909.

Application :ined ft'iigust e, 1905. fleris'l No. 272 S93.

l o all 'who/m 'it may omer-7i.: l Se it known that l, HARRY E. Hnfi'rn, could he done and that not only large easteitizen ol the Umted States, residing etv ings could oe made but that crystalline siht was .found that this Lynn, county of Essex, and State of Massaf con oould be east into small pencils not ei;-

died. Upon trial i .J ehusetts, have invented certain new and usei ceeding one-quarter of an inch in diameter. o lu'limproyements in Rlieostats, of which the It was found moreover, that the resistance "lol'lovymg is a speiieation. of these cast units is nearly Constant und that This invention relates to resistance units upon increase in temperature up to ti red for electric Circuits and .has for its object the i heat, the resistance increased Very slightly.

, The spe iiic resistance of these units being of) twice that of carbon, the units may he small and compact. I have also found that a cast unit can be heat-ed to a red heat and sudl denly Cooled by plunging;` .in writer Without croc-king.;` or disintegratingV it. These prop- 'r erties render the unit a Very desirable one as Y substitute for the wire, graphite and car- Coli or any convenient form, n'oyiding the l hon resistance, it being pt ble to construct ysame With termina-ls for oonneetion with the l a Very compact, cheap, o'ilieient and durnhle eleetrie circuit. Units of this charaoterhave l rheostat of these cast unit-s. For purposes 7 l l l aoter which will be practically indestructible While atl the same time occupying. minimum of space and capable of being produced at a very tow oost.

heretofore, it has been the common practice to use e resistance conductor Wound into a not vbeen entirely satisfactory owing 'to the of illustration, therefore, l haveshown my feet that they ere ensily destroyed, :is ior in` improved resistance unit in connection with stance, hy being burned out. They ere lilies rheostat, but it should he-understood that wise expensive to construct and occupy more i i do not limit my invention tothis particular space in proportion to the resistance o-terod use since it is capable of wide applica-tien. Se than is oftentimes desirable. i' My invention, therefore, is only limited oy Resistance units have also been propose l the scope of the Claims annexed to and formwhioh are made of east material surh as cast Q ing' port of this application. y iron in the form. of grids, and also of molded ln the drawings, Figure l is a plan View of a rheostzit embody/infnT my improvements; 8.3 stitute what are known as stichA resistances. Fifi'. 2 is an elevation of the same; Fig. o is a These cast end molded units have heen plan Yiew of a modified form of my invenfonnd to he objections-hln for many reasons l tion; Fig. el is an elevation of the seme; Fig. and their use has therefore been greatly lim 5 shows one of the resistanue units used. in

l the modified torni of my invention; Fig. 6 is 9o eiiio resistance is so low that the apparntus l nn end elevation ofthe same; and Fig. 7 is a requires oonsiderzihle space and moreover, i seetionnlyiew taken on theline T-T ollfig. 5. since the. material is oxidizahle, the life is Referringv to the drawings (Figs. l and 2), short incase the tenipernture is raised shore an insulating: hase of any desired ma- 40 the normal. 'These ohjections also appl.v teria-l. counnonly used in devices of this char- J5 .15 heating and cooling. t has heen found that i3 regular forms so as to he conveniently hanto the molded graphite und carbon resist l prefer, however, to employe. base nnoes which .have a fui .er objection in that 'st iron which is insulated by' means of`V the roeilicients of expansion nre such ns to the Coating of enamel. Mounted upon this cause the nnit to disintegrate by repented insulatinghnse is a pairof resistance units 2 secured to the hase hy means of the bolts 3. loe These units are east from the element silicon into the form of an. are and mounted as shown so :is to practically form a circle. A

the element silirj'on hns s. speeiiic resistance .nearly twice that. ,of ordinary carbon hut that unlike cui-hon, it is fdile to withstand a l red heat without oxidation. Moreover, its brush arm 4 is pivoted at 5 so that its free expansion eoeflicient is lou', and it` will not l ends engage the units 2. rThe arm 4 is held. 10.3 disintegrate under changes of temperature. in yielding contact with the units by means of in order to place this element. into a desirable 1 the spring 6 secured to the pivot helt. The form for resistance units it occurred to me ,l bolts 3 serve as terminals tor the units which that the element might possibly he cast into l may he eleotroplated or otherwise treated at l the ends to make goed eleetrionl Contact. A I in starting handle 7 is secured to the control ling arm by means ol which the latter may be moved so as to vary the amount of resistance in circuit in a well-known manner. By moving the arm to the right from the position shown in Fig. 1, resistance is gradually cut out of circuit while by moving it to the lel't the resistance is out in. ln this form of my device, the variation of resistance is gradual and a very fine vregulation may therelore he obtained.

ln Figs. 3 to 7, l have shown a modified form 'in which a step-by-step variation 1s produced. Rel'errmg to these ligures, 8 1s a box yof suitable material provided with an insulating cover 9 which serves as a base for the rheostat. A series of resistance units 10 are mounted upon the base and arranged in the form of a circle with 11 as a center. A brush arm 12 is pivoted at 11 so that its free end moves over and successively engages the units 1() to cut them in or out of circuit in a well-known manner. '.lhese units 1U, l pre.- i'er to cast from silicon in the form shown in Figs. 5 to 7. l cast them into a Ueshaped lorm, the cross-section of which is oval as shown in Fig. 7. The enlarged ears 18 are provided for making Contact with the arm l2. The units are connected in series by means of the clips 14 which connect the units through the shouldersv 15. The resistance may be therefore, increased or decreased by moving the arm 12 to the left or right as desircd, to successively out in or out the resistance units. lt will, therefore, be seen that l have shown two forms of rheostats which embody my improved resistance unit, one of which provides for successively cutting out the units and the other provides for gradually varying the extent ol' a single unit. it

not limit myself to `these forms of rheostats, nor do I limit the use of my resistance unit to'its application to a rheostat, as many other uses Will suggest themselves to those skilled in the art.

What I claim as new, and desire to secure by Letters Patent of the United States, is,-

1. A resistance unit of .east silicon provided with a contacting terminal.

' 2. A resistance unit consisting ol a body ol cast silicon having an ailixcd terminal thereon. l

3. A resistance unit consisting of a body of cast silicon oi uniform cross-section.

4. A resistance unit consisting of a body ol uncombined silicon in crystalline form cast in regular shape. l

5. A rhoostat comprising a cast silicon unit, and a controlling arm mounted for engagement therewith.

6. A rheostat comprising a cast silicon unit, and a controlling arm mounted for slid` ing engagement therewith. 4

ln witness whereof, Iillave hereunto set my l hand this first day of August, 1905.

HARRY E. l-IEA'lll. Witnesses:

JOHN A. MCMANUS, Jr., HENRY O. 'WESTENDARR should, however, be understood that I do 

